My opinion:
One possible scenario I can think of would be she was abducted while she was out bike riding, since they found her bike tossed down a slope.
Another less likely possibility would require looking at the phone of that "married with children" man she was having an affair with. Conceivable she could have implemented her plan to disappear in South America to meet up with the guy. Maybe she tossed her phone and bought a burner phone or a new phone to carry out her plan, paying for everything in cash. Maybe the guy came to his senses and decided he didn't want to abandon his family and embark on such a course. Could something have happened to her in South America? I don't think this is likely because SM's children have not heard from her, but would still like to know his phone shows no further contact with her or that he didn't get a new phone where contact is continuing.
In my opinion, without some solid evidence BM killed her, there is room for reasonable doubt. My opinion and conjecture.
"It is better that ten guilty persons escape than that one innocent suffer" -- English jurist William Blackstone, "Commentaries on the Laws of England", 1760.
Barry was literally the only person who could have been responsible.
A crumbling marriage, a threat of suicide, deleted texts, and a lie about the "perfect marriage."
Suzanne's digital footprint suddenly ceases, while she's talking to her lover and snap chatting her best friend. This breaks all established patterns.
Barry attempts to explain this away by describing the perfect night, in which they eat two steaks off two plates (like normal people), then one steak off two plates, and finally, one steak off one plate.
Then they make love and go to bed.
During this time his truck moves, his phone comes out of airplane mode, his phone shows 200 events (as opposed to the usual 0-2), his truck doors are opening and closing, his screen comes on, his phone is moving, her phone is moving, and Suzanne's phone powers down forever at the precise moment he needs it to.
He wakes to the alarm that he set, then he did not set. He drives straight to Broomfield, then makes a detour months later, when he's framed by a herd of elk that lead him right past the location of Suzanne's helmet.
SA Harris played him like a fiddle here, planting the idea in Barry's head that the truck telematics proved he was lying. Barry responded by once again changing his story to fit the evidence, a hallmark of murderers.
Not only is there no evidence of a bike ride, but there is overwhelming evidence it did not occur.
Miles Harvey said she wouldn't bike there. She didn't bring items she'd always bring. She would have had to have taken her powered down phone with her, which she uncharacteristically hadn't used for hours, and didn't use on that very important morning (Mother's day, best friend daughter's wedding, her daughters traveling home, etc).
Barry arrives in Broomfield, and spends all day traveling back and forth from the hotel and the wall.
Just kidding, that was a lie. He visited the wall once, and claimed he had time to kill so he dumped trash in 5 different receptacles.
The fact that 4 of these 5 dumps came prior to that, notwithstanding.
The Ritters call him, and he tells them he's "at the wall, with workers present."
Of course there were no workers, and he'd been in his room for 5 hours.
He repeats this lie to CBI multiple times, telling them he rushed from the wall back to his hotel room, where he left tools in the lobby.
Surveillance video proves this unequivocally to be the lie to end all lies. He leaves his room, stages tools in the lobby to make it appear he'd been working, and then hits the road.
The following day he speaks to Morgan on the phone, telling her that a lion got Suzanne. Then he encourages her to keep working, as it helps sell his alibi (this is really transparent and damning).
Nine months after the investigation began, Barry suddenly remembered that he had been chasing chipmunks around the backyard with his 22 rifle, when he arrived home on the day in question. He did this in response to phone data, that showed his phone moving erratically.
When Suzanne's Facebook began making friend requests in the days preceding her murder, Barry blamed a bear or a coyote for why his phone happened to be down by the river during this period.
To explain away the needle sheath in the dryer, Barry claimed to have shot two deer just weeks before, and illegally sawed their antlers off. This, despite previously claiming to have never fired a tranquilizer gun in Colorado.
Killers have a habit of confessing to lesser crimes, and Barry did this here, and when he suggested "immunity."
To explain his phone and truck indicating that he was creeping around the backyard on the afternoon of the murder (when he was supposedly having lunch with Suzanne), Barry blamed a long dead Turkey that he claimed to be searching for.
Of course Suzanne texted JL just prior, saying Barry wasn't home. His truck and phone show that he didn't enter the house, the meal he claimed to eat was from a day or two before (a little bit of truth..) and he called Suzanne minutes after sitting down with her for lunch (he clearly never entered the house)
When Barry initially arrived on scene, he immediately began attempting to cast suspicion towards a mountain Lion. He repeated this claim for months, offering it as a possibility to both investigators, and a reporter.
The average person knows that mountain lions don't commit bloodless kidnappings, toss bikes in ravines, and remove helmets and dump them a considerable distance away.
As a hunter and outdoorsman, Barry's actions are far more incriminating. Not only did he repeat this (Lion) scenario months later, but he kept searching the immediate area for months.
It allowed him to save face in regards to not doing anything to find his missing wife, while he got to enjoy the outdoors.
An innocent person doesn't have to lie about anything, and Barry lied about everything. Lies absolutely matter.
So to believe Barry is innocent, one would have to exhibit stunning ignorance, and then put stock in a theory for which there is not only no evidence, but no precedent:
Suzanne was kidnapped by a lion from "The Ghost and the Darkness."
A "Gone Girl" frame job on steroids.
The luckiest kidnapper on earth, who managed to get the prime suspect to tell lie after lie, and took advantage of dozens of coincidences.
In terms of factual guilt, I genuinely can't think of many cases this cut and dry.
There is no plausible alternative scenario, and no scenario that explains away all the evidence against Barry.
Everyone knows the husband is looked at first, and that's what happened here. He should have been able to be cleared very quickly, as any sign of life when he left that morning means he couldn't have killed her.
But that's when they hit a major hurdle in that regard, as not only was there no sign of life that morning, but there was no sign of life hours before that (extending back to the previous afternoon).
Barry's alibi was the most damning thing I've ever seen, from the Fotis Dulos like trash dumps, to the insane lie about his movements.
That hotel was full of cameras, and this moron had the gall to lie about where he was when he got that phone call from the Ritters.
The worst part is the lies started before he ever should have known a crime was committed.